- Assume that . Prove that the perpendicular distance from to the line passing through the points and is given by the formula
- Compute the distance in the case

*Proof.*We know the area of the parallelogram determined by and is given byBut this is exactly twice the area of the triangle with base and height the perpendicular line from to the line through and . Hence, is the perpendicular distance from to the line through and , and

- When we have